Kidney Function: Tubular Reabsorption and Filtration. G28

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary mechanism responsible for the initial movement of sodium across the basal outer membrane?

Primary active transport (correct)

Facilitated diffusion

Secondary active transport

Simple diffusion

Which of the following statements accurately describes the role of the sodium potassium ATPase pump in glucose reabsorption?

The pump provides energy for the secondary active transport of glucose by maintaining an electrochemical gradient. (correct)

The pump acts as a co-transporter for sodium and glucose.

The pump is responsible for the passive diffusion of glucose.

The pump directly transports glucose across the membrane.

What is the main driving force for the secondary active transport of glucose in the proximal tubule?

The electrochemical gradient of sodium (correct)

The concentration gradient of glucose

The osmotic pressure of the interstitial fluid

The hydrostatic pressure in the tubular lumen

Which of the following is TRUE regarding the transport of glucose at the basal lateral side of the proximal tubule?

Glucose is passively transported down its concentration gradient by a protein known as glute 1. (C) Signup and view all the answers

Which statement best explains why glucose reabsorption in the proximal tubule is considered secondary active transport?

The movement of glucose across the membrane is dependent on the energy derived from sodium transport. (D) Signup and view all the answers

What is the primary mechanism responsible for the movement of amino acids from the tubular lumen into the tubular cell?

Secondary active transport driven by the sodium gradient (B) Signup and view all the answers

What is the significance of the SGLT1 and SGLT2 transporters in the context of glucose reabsorption?

They function as co-transporters for sodium and glucose, contributing to the secondary active transport of glucose. (A) Signup and view all the answers

If the sodium potassium ATPase pump was inhibited, what would be the most likely outcome for glucose reabsorption in the proximal tubule?

Glucose reabsorption would decrease significantly due to the lack of an electrochemical gradient for sodium. (C) Signup and view all the answers

What is the primary force driving the uphill movement of hydrogen ions during secondary active transport in the proximal tubule?

The downhill movement of sodium ions. (D) Signup and view all the answers

Which of the following statements accurately describes the relationship between transport maximum and filtered load?

Transport maximum is initially proportional to filtered load, but plateaus once a certain threshold is reached. (D) Signup and view all the answers

What is the primary mechanism responsible for the appearance of glucose in urine when the filtered load exceeds the transport maximum?

Saturation of carrier proteins and specific enzymes involved in glucose reabsorption. (B) Signup and view all the answers

The transport maximum for glucose is approximately 375mg/minute. What does this value represent?

The maximum amount of glucose that can be reabsorbed by the kidneys in one minute. (C) Signup and view all the answers

Why does glucose excretion in urine occur before the transport maximum is reached?

Not all nephrons have the same transport maximum, leading to some nephrons reaching their limit before others. (A) Signup and view all the answers

Which of the following substances is NOT likely to demonstrate a transport maximum?

Sodium ions (B) Signup and view all the answers

What is the relationship between the sodium-hydrogen exchanger protein and the reabsorption of hydrogen ions?

The protein directly transports hydrogen ions out of the cell, leading to their secretion. (D) Signup and view all the answers

What is the primary difference between secondary active transport and primary active transport?

Secondary active transport uses an electrochemical gradient, while primary active transport uses ATP directly. (C) Signup and view all the answers

In which part of the nephron is the rate of sodium reabsorption primarily determined by the concentration gradient in the tubular lumen?

Proximal tubule (B) Signup and view all the answers

Which of the following MOST ACCURATELY explains why the transport of sodium in the early proximal tubule is not limited by a transport maximum?

The reabsorption of sodium is mainly driven by the electrochemical gradient, not by a specific transport protein. (B) Signup and view all the answers

What is the primary factor responsible for the movement of water across the tubular epithelium in the proximal tubule?

Osmosis driven by the solute concentration difference between the tubular lumen and the renal interstitium. (C) Signup and view all the answers

Which of the following statements BEST explains the relationship between transport maximum and hormone regulation?

Hormones directly influence the transport maximum by changing the number of transport proteins present. (D) Signup and view all the answers

Which of the following conditions would MOST LIKELY lead to an increase in the rate of sodium reabsorption in the proximal tubule?

An increase in the concentration of sodium in the renal interstitium. (C) Signup and view all the answers

What mechanism primarily allows for the reabsorption of large molecules such as proteins in the proximal tubule?

Pinocytosis (B) Signup and view all the answers

How does a decrease in tubular reabsorption impact urinary volume?

It dramatically increases urinary volume. (A) Signup and view all the answers

Which substances are typically reabsorbed almost completely in the renal tubule?

Glucose and amino acids (B) Signup and view all the answers

What type of transport does pinoctosis use, and how does it relate to energy consumption?

Active transport; it requires energy. (A) Signup and view all the answers

What primarily determines whether a substance will be filtered through the glomeruli?

Its binding affinity to plasma proteins (D) Signup and view all the answers

In what manner is tubular reabsorption described in the content?

Variable and highly selective (A) Signup and view all the answers

How are substances transported during reabsorption from the tubular lumen to the blood?

Via the renal interstitium and capillary membrane (D) Signup and view all the answers

Which of the following waste products is poorly reabsorbed, resulting in its large amounts in urine?

Urea (A) Signup and view all the answers

What role do hydrostatic and colloid osmotic pressures play in the transport of solutes in the blood?

They mediate the movement of solutes similar to venous pressures. (C) Signup and view all the answers

Which statement accurately describes the process of active transport?

It requires energy to move solutes against their electrochemical gradient. (B) Signup and view all the answers

How does secondary active transport differ from primary active transport?

Secondary active transport relies on an established ion gradient. (C) Signup and view all the answers

In the sodium-potassium ATPase pump mechanism, what is the primary function?

To maintain a low intracellular concentration of sodium. (B) Signup and view all the answers

What is the significance of the tight junctions between epithelial cells?

They provide structural support and regulate permeability. (D) Signup and view all the answers

What happens to sodium ions during the process of secondary active transport involving glucose?

They diffuse from the tubular fluid into the cell, bringing glucose with them. (B) Signup and view all the answers

Which fluid is primarily responsible for solute transport between the cell junctions?

Interstitial fluid (A) Signup and view all the answers

What occurs during venous reabsorption?

Solutes are reabsorbed into the blood through hydrostatic pressure. (D) Signup and view all the answers

What is the role of the sodium-potassium ATPase pump in tubular epithelial cells?

It creates a negative intracellular charge by actively transporting sodium out of the cell. (D) Signup and view all the answers

How is sodium primarily reabsorbed in the proximal tubule?

Through both transcellular and paracellular pathways. (C) Signup and view all the answers

Which factor contributes to the concentration gradient for sodium reabsorption?

Low intracellular sodium concentration maintained by the sodium-potassium pump. (A) Signup and view all the answers

What effect does the extensive brush border have on sodium reabsorption in the proximal tubule?

It multiplies the surface area for reabsorption by about 20-fold. (D) Signup and view all the answers

What is the typical sodium concentration inside tubular epithelial cells?

12 mM (C) Signup and view all the answers

Which statement accurately describes the transcellular pathway of sodium reabsorption?

Sodium primarily enters the cell through the apical membrane down an electrochemical gradient. (B) Signup and view all the answers

What represents the electrochemical gradient's effect on sodium transport in tubular epithelial cells?

It drives sodium into the cell due to a negative internal charge. (C) Signup and view all the answers

Which process enhances sodium transport in the proximal tubule aside from the sodium-potassium pump?

Carrier proteins that facilitate diffusion. (C) Signup and view all the answers

Study Notes

Tubular Reabsorption

Large molecules like proteins are reabsorbed in the proximal tubule via pinocytosis.
The proteins are digested into amino acids, which are then reabsorbed.
This process requires energy, making it active transport.

Filtration

Filtration is non-selective.
Substances not bound to protein are filtered.
The amount filtered depends on its plasma concentration.
Glomerular filtration is significantly higher than urine output, leading to high tubular reabsorption.
A small change in filtration or reabsorption can cause a large change in urinary output.
A 10% decrease in reabsorption can increase urinary volume from 1.5 to around 19.3 liters per day.

Tubular Reabsorption Mechanisms

Reabsorption is highly selective.
Substances like glucose and amino acids are almost completely reabsorbed.
Sodium and chloride reabsorption is variable.
Waste products like urea are poorly reabsorbed and excreted in large amounts.
Reabsorption utilizes transcellular or paracellular pathways.

Active Transport

Active transport moves substances against their electrochemical gradient, requiring energy, often from ATP.
The sodium-potassium pump is an example of active transport, which moves sodium out of the cell and potassium into the cell.

Secondary Active Transport

Secondary active transport is indirectly coupled to energy sources.
Sodium potassium pump builds a concentration gradient for sodium.
Glucose and amino acids are reabsorbed via secondary active transport, transported with sodium ions across the membrane.

Transport Maximum

There's a limit to the rate of active reabsorption.
Carrier proteins and specific enzymes involved saturate when the filtered load exceeds the capacity of the tubule for reabsorption.
Glucose reabsorption has a maximum rate, and excess glucose is excreted when filtered load exceeds capacity.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the processes of tubular reabsorption and filtration within the kidneys. Learn how large molecules like proteins are handled and the significance of selective versus non-selective filtration. Understand the implications of these processes on urinary output and overall kidney function.

Kidney Function: Tubular Reabsorption and Filtration. G28 - 1

Choose a study mode